1. Field of the Invention
The present invention relates to an electromagnetic fluid controller that controls the opening and closing of a fluid passage by using an electromagnetic drive.
2. Description of the Related Art
A conventional type of an electromagnetic fluid controller 400 is known and is shown in a cross-sectional view in FIG. 9. In this controller, upon energization of a coil 46, an armature 31 is attracted by an electromagnetic force generated at a stator 40, and then a valve needle 30 in one body with the armature 31 turns from being seated in a valve seat (not shown) formed at one end of a valve body 20 to being separated from the valve seat so that a fluid passage is opened.
FIGS. 10A and 10B are enlarged partial cross-sectional views showing the motion of the armature 31 having the fixed valve needle 30 in FIG. 9, where FIG. 10A and FIG. 10B respectively show the state during deenergization and the state during energization.
As shown in FIG. 10B, an air gap (also referred to as a final air gap) GA is provided so that the armature 31 will not abut the stator 40 directly when it is attracted by the stator 40 upon energization of the coil 46. Air gap GA prevents an action force of magnetic attraction, which can be generated upon deenergization of the coil 46, between both the magnetic metallic material members of the armature 31 and the stator 40 in order to reduce the effect of a delay in the timing of the separation of the armature 31 from the stator 40.
In the above described controller, when the state changes from deenergization of the coil 46 shown in FIG. 10A to its energizaton shown in FIG. 10B, the armature 31 is attracted and moved to the side of the stator 40 with the lift amount DL. At the ending position of this motion, the top face of the valve needle 30 abuts the bottom face of a bearing 37, whereby the air gap GA is secured between the armature 31 and the stator 40. At this moment, an end face of the armature 31 faces to an end face of the stator 40, having an air gap GA without abutting it directly.
To provide a structure having the foregoing air gap GA, a difference in level, between the top face of the valve needle 30 abutting the bottom face of the bearing 37 and the top face of the armature 31 facing the stator 40, is to be applied in machining a specified dimension, which results in the disadvantage of higher manufacturing costs.
Furthermore, to be durable against shock loads applied by repeated motion, in addition to the press-fitting of the valve needle 30 and the armature 31 to each other, they are connected by laser welding, as indicated by the ‘black colored triangle’ mark in FIG. 9 and FIGS. 10A and 10B, or the like, which results in increased manufacturing costs.